In recent decades, the use of internal combustion engines, powered by the ignition of hydrocarbon fuel, for transportation and energy generation has become more and more widespread.
For example, compression ignition engines, which will be referred to further as “diesel” engines after Rudolf Diesel (who invented the first compression ignition engine in 1892) feature among the main type of internal combustion engines employed for passenger cars and heavy duty applications, as well as for stationary power generation, as a result of their high efficiency. In a diesel engine a fuel/air mixture is ignited by being compressed until it ignites due to the temperature increase resulting from compression.
It has been found that the addition of viscosity index (VI) improving additives to diesel fuel has significant benefits. WO2009/118302, for example, discloses the use of VI improving additives, in an automotive fuel composition, for the purpose of improving the acceleration performance of an internal combustion engine into which the fuel composition is or is intended to be introduced. The concentration of the VI improving additive may be up to 1% w/w, although optimum concentrations are said to be, for instance, between 0.05 and 0.5% w/w, or between 0.05 and 0.25% w/w, or between 0.1 and 0.2% w/w.
VI improving additives may be dosed (or added) directly into a fuel component or composition, for example at a refinery. Alternatively, VI improving additives may be pre-dissolved to form an additive composition or pre-blend, which is subsequently dosed into the fuel component or composition. Pre-dissolution has the advantage of leading to a more even distribution of the VI improving additive in the fuel. Furthermore, the blending of base fuel components may not be feasible at all locations, whereas the introduction of additive compositions, in relatively low amounts, can more readily be achieved at fuel depots or at other filling points such as road tanker, barge or train filling points, dispensers, customer tanks and vehicles.
WO2009/118302 suggests a number of examples of solvents that may be used to pre-dissolve VI improving additives in general, including certain fuel components and organic solvents.
Nevertheless, there remains a need for compositions and methods that facilitate the blending of VI improving additives, specifically VI improving polymers, into fuel in an effective and convenient manner.